Correctly fetch the ips from server

In _check_tenant_network_connectivity(), server's ips are not fetched
correctly. Current code throw KeyError as mentioned in bug.

This patch fix the above issue.

Change-Id: Ibf9b3997b927a66c507f04e2671faf9cb8581ff3
Closes-Bug: #1401028
Merge "Correctly fetch the ips from server"